1. Field of the Invention
The present invention relates to molecular press dehydrating agents and a molecular press dehydration method for vegetative tissues using the same. Dehydration method of vegetables is a very useful technology in the fields of foods and beverages, feeds, cosmetics and pharmaceuticals industries.
2. Description of the Prior Art
Traditional dehydration and drying methods of vegetative tissues include osmotic dehydration, hot air drying, freeze drying, etc. Osmotic dehydration includes salting method and sugaring method using salts such as the table salt and using sugars such as sucrose as dehydrating agents respectively.
This method has an advantage in that the initial dehydration rate is high. However, the final amount of dehydration is small, and a large amount of the dehydrating agent permeated into the cell wall affects the taste and quality of dehydrated tissues adversely. Further, this method is disadvantageous in that the dehydrating agent lowers rehydration quality of tissues after drying because it denatures cell wall components during dehydration
Hot air drying is a traditional dehydration method for vegetative tissues by heated dry air. This method is advantageous in economical aspect, but it is difficult to be used for processing high-grade food because the heat deteriorates the quality such as colors, flavors and texture of dehydrated tissues.
In freeze drying method, the quality of food is maintained excellently since food components are less changed compared to other methods. However, the texture of tissues is damaged greatly since cell tissues are destroyed by freezing. Due to high processing cost, this method is only applied to some high-grade foods.
For the above reason, the present inventor developed molecular press dehydration method and applied it for a patent that is a new technology for the dehydration of vegetative tissues. The molecular press dehydration method depends on cytorryhsis phenomenon. Cytorrhysis is a phenomenon of enforcing dehydration of the cell by contraction where the polymers, if their sizes are greater than those of the pores of the cell wall, are unable to be permeated into the cell wall, and the cells are contracted and distorted by the diffusion pressure of polymer molecules applied to the cell wall outside, when vegetative tissues are in the concentrated solution of those water-soluble polymers.
A large amount of moisture can be dehydrated by molecular press dehydration method compared to osmotic dehydration. Moreover, the molecular press dehydration method does not deteriorate components in the cell including cell wall, and facilitates drying followed by molecular press dehydration, and has lesser adverse effects on taste and flavor of tissue. Also, the dried tissue by this method can be restored in the state of almost fresh tissue when rehydrated with water. Because a large amount of dehydrate exudated in the process of molecular press dehydration is not in dilution with added water, the useful component is highly concentrated and flavor is almost natural. And high concentration of dehydrating agent eliminates spoilage by microorganisms and deterioration by oxidation considerably, therefore it raises the utilization of dehydrate.
The substances used for the dehydrating agents in molecular press dehydration method should be water soluble polymers which has a molecular size greater than the pore size of the cell wall of plant cells, therefore they make a molecular diffusive pressure only outside the cell, and should maintain gradients in concentration of dehydrating agents in and out of the cells continuously.
The present inventor has disclosed various soluble polymers which can be used for the dehydrating agents in this molecular press dehydration method of Korean Patent Application No. 10-2001-69777.
For example, the water soluble polymers such as PEG (polyethylene glycol), gum arabic, arabinogalactan, egg albumin, milk proteins or soy proteins could be used for molecular press dehydration of various plant tissues efficiently, but these polymers have kinds of inherent problems as followings.
PEG is a synthetic polymer substance with a great solubility in water and the viscosity of water solution of PEG is low. Therefore PEG is the best substance among the above dehydrating agents for molecular press dehydration method. But, owing to the fact that PEG is a chemically synthesized compound, there are some legal limitations on food use, and average consumers are concerned about the acceptance of it.
Gum arabic, arabinogalactan, and egg albumin are easily soluble in water and the viscosity of the water solution is low. And they are natural substances, so they are suitable molecular press dehydrating agents for food use. But, compared to PEG, they have a less dehydrating efficiency, and make dehydrated products of quite low quality, and are less economical due to higher prices. Particularly, gum arabic and arabinogalactan may bring about a short supply when they are used in large quantities. In case of egg albumin, the exudates can be easily spoiled by microorganisms during dehydration and storage after dehydration.
Milk proteins and soy proteins are advantageous in that they are natural sources which can be supplied in large quantities, but they have a lot of problems in practical use because the above proteins generally available at the present time are less soluble in water, and the viscosity of their water solutions are rather great.
As mentioned above, when vegetative food materials are dehydrated and dried only with the above molecular press dehydrating agents, there are problems in respects not only of regulations, social acceptance and economy but also of supply. Accordingly, there remain subjects to study and develop molecular press dehydrating agents which can be supplied in large quantities while being of natural origin.
Proposed in the present invention is molecular press dehydrating agents and an effective method of dehydration of vegetative tissues with a high yield of dehydration, without application problems in respects of regulations, social acceptance and economy, and capable of being supplied smoothly and in large quantities.